When calculating the number of treads and height of risers for a staircase, which two measurements are required?

• A. Total length and width
• B. Total run and total rise
• C. Riser height and tread depth
• D. Number of stringers and landings

Answer: (B)

The task hinges on two overall distances: how far the stairs must run horizontally (the total run) and how far they must rise vertically (the total rise). Knowing these lets you figure out both how many steps you need and how tall each step should be.

The total run is the horizontal distance from the start of the stairs to the landing. If you choose a comfortable tread depth, you divide this run by that depth to estimate the number of treads. The total rise is the vertical distance from the bottom floor to the top floor. Dividing this rise by a typical riser height gives the number of risers. In standard stairs, the number of risers roughly equals the number of treads, so these two measurements drive the whole count-and-height setup.

Other measurements like width or the number of stringers influence support and space, but they don’t by themselves determine the count and height of each step.